Continuous squeeze-dewatering device

ABSTRACT

A continuous compression-type dewatering apparatus has a filter chamber ( 3 ), a drive shaft ( 17 ), a vane ( 15 ), and a supply path ( 50 ). The filter chamber ( 3 ) is delineated by an annular plate ( 2 ) and two side plates ( 1, 1 ). The drive shaft ( 17 ) passes through the center axis of the annular plate ( 2 ) and through the inside of the filter chamber ( 3 ), and is free to rotate with respect to the filter chamber ( 3 ). The vane ( 15 ) is disposed within the filter chamber ( 3 ), is fixed with respect to the drive shaft ( 17 ), and rotates in concert with the drive shaft ( 17 ). The supply path ( 50 ) passes through the drive shaft ( 17 ) and supplies raw fluid to the filter chamber ( 3 ). The vane ( 15 ) as two side edges ( 15   a   , 15   a ) facing the side plates ( 1, 1 ) and an end edge ( 15   b ) facing the annular plate ( 2 ). The side plates ( 1, 1 ) include a screen ( 4 ) for separating the raw fluid into a filtered fluid and a cake. The annular plate ( 2 ) includes an ejection port ( 7 ) for the cake. Inflow pressure of the raw fluid from the supply path ( 50 ) into the filter chamber ( 3 ) and rotation of the vane ( 15 ) causes the filtered fluid to flow out from the filter element ( 4 ) to the outside of the filter chamber ( 3 ), a cake that remains inside the filter chamber ( 3 ) being pushed to the outside of the filter chamber ( 3 ) via the ejection port ( 7 ).

This application is a 371 of PCT/JP99/05077 filed on Sep. 17, 1999 whichhas been published as WO00/16970 on Mar. 30, 2000, and claims thepriority benefits of Japanese applications, P10-263014 filed on Sep. 17,1998 and P10-296477 filed on Oct. 19, 1998.

TECHNICAL FIELD

The present invention relates to a continuous compression-typedewatering apparatus for concentrated sludge, and more particularly to acompression-type dewatering apparatus for sludge that is difficult tofilter, such as sewage sludge.

BACKGROUND ART

A filter press, a belt press, and a screw press (refer to JapanesePatent Application Publication No. 44-2929 and Japanese UnexaminedPatent Application Publication No. 6-695, for example) are known typesof pressurized dewatering apparatuses for dewatering difficult-to-filtersludge, such as sewage sludge.

With a filter press, however, there is a tendency for clogging to occurin the filter cloth used as a filter material, and it is difficult torenew the filter cloth by cleaning.

With a belt press, in order to sustain the functions of the filter clothused as a filter material, it is necessary to continuously clean thefilter cloth as dewatering is performed. For this reason, a large amountof cleaning water is consumed. Additionally, because sludge is onlypressurized at the outer peripheral surfaces of a large number ofpressure rolls arrange in a line, a large amount of installation spaceis required, and the filtering efficiency is low.

With a screw press, because the filtering surface is divided on theinner surface of a cylindrical metal filter material, a large amount ofinstallation space is required, and the filtering efficiency is low.

DISCLOSURE OF THE INVENTION

In consideration of the above-described problems occuring in the past,it is an object of the present invention to provide a continuouscompression-type denaturing apparatus having simple construction, smallsize, and a small installation space, and which has a high filteringefficiency, and operates at a low speed, so as to require only a smalldrive source.

To achieve the above-noted object, a first aspect of the presentinvention has a filter chamber (3), a drive shaft (17), vanes (15), anda supply path (50). The filter chamber (3) is divided into an annularplate (2) and two side plates (1, 1). The drive shaft (17) passesthrough the center axis of the annular plate (2) and through the insideof the filter chamber (3), and is freely rotatable with respect to thefilter chamber (3). The vanes (15) are disposed within the filterchamber (3), are fixed with respect to the drive shaft (17), extend fromthe drive shaft (17) toward the annular plate (2), and rotate in concertwith the drive shaft (17). The supply path (50) passes through theinside of the drive shaft (17) and supplies raw fluid to the filterchamber (3). The vanes (15) have two side edges (15 a, 15 a) that facethe side plates (1, 1) and an end edge (15 b) that faces the annularplate (2).

At least one of the side plates (1, 1) includes a filter element (4) forseparating the raw fluid into a liquid and a cake. The annular plate (2)includes an ejection port (7) for the cake.

By the action of the inflow pressure of the raw fluid from the supplypath (18) to within the filter chamber (3) and the rotation of the vane(15), the filtered fluid flows out f rom the filter element (4) to theoutside of the filter chamber (3), a cake that remains inside the filterchamber (3) being pushed to the outside of the filter chamber (3) fromthe ejection port (7).

In the above-noted configuration, the raw fluid flows into the centerpart of the filter chamber (3) from the supply path (50). After havingflowed into the filter chamber (3) the raw fluid receives the flowpressure thereof and moves toward the side plate (1), and is filtered bythe filter element (4). The filtered fluid passes through the filterelement (4) and is ejected from the filter chamber (3), the cakeremaining on the filter element (4). The remaining thin film of cake isscraped by side edge (15 b) of the rotating vanes (15), and is senttoward the outer periphery by the vanes (15). When the cake moves, arotational friction force develops between the cake and the vanes (15),so that sliding resistance is generated between the cake and the sideplate (1). For this reason, the cake is further filtered as it moves, sothat the water content is lowest in the region of the annular plate (2).The cake with low water content is ejected via the ejection port (7).

The filter element (4) can be provided on each of the side plates (1),and can be provided over substantially the entire area of the side plate(1). By doing this, the filtering surface area with respect to the rawfluid is increased, thereby further increasing the filtering efficiency.

The annular plate (2) can include a second filter element (9) forseparating the raw fluid into a liquid and a cake. By doing this, thefiltering surface area with respect to the raw fluid is increased,thereby further increasing the filtering efficiency. The cake on thefilter element (9) is pressured by the end edge (15 b) of the vane (15)and further dewatered, so that a cake with a further decreased watercontent is ejected from the ejection port (7).

The filter element (4) can be a substantially donut-shaped screen (4)with a large number of fine holes. The second filter element (9) can bea screen (9) with a large number of fine holes.

The side plate (1) can have a screen (4), an annular outer frame (5)fixed to the outer peripheral edge of the screen (4), an annular innerframe (6) fixed to the inner peripheral edge of the screen (4), and arib (5 a) that links the outer frame (5) and the inner frame (6). Bydoing this, mounting of the screen (4) to the side plate (1) isfacilitated, and the strength of the screen (4) is increased.

The supply path (50) can have a main supply path (18) within the driveshaft (17), a supply port (19) formed in the drive shaft (17) that openstoward the main supply path (18), and a linking path (11) adjacent tothe drive shaft (17) on the side of the vane (15) and linking the supplyport (19) and the filter chamber (3).

In the above-noted configuration, the raw fluid flows from the mainsupply path (18) through the supply port (19) and the linking path (11)into the filter chamber (3) from the side of the vane (15). The positionof the supply port (19) is not particularly restricted, as long as it ison the side of the vane (15). In contrast, in the case in which the rawfluid is directly supplied from the main supply path (18) into thefilter chamber (3), it is necessary that a port for supplying be formedin the part of the drive shaft (17) facing the filter chamber (3).Therefore, in order that the vane (15) be securely fixed by the driveshaft (17), there is the possibility of an increase in the materialthickness of the drive shaft (17). When the material thickness of thedrive shaft (17) increases, this can bring with it an increase in theweight and size of the apparatus.

With regard to this point, according to the above-noted configuration itis possible to form the supply port (19) at a location that does notpresent a problem with regard to strength, thereby limiting the increasein weight and size of the apparatus.

The vanes (15, 63, 65, 67) can have operative surfaces that are forwardin the rotational direction of the drive shaft (17), and the linearshape of the operative surface on a cross-section perpendicular to thedrive shaft (17) can be substantially the same, and not dependent uponthe location on the cross-section in the axial direction of the driveshaft (17).

The operative surface (52) on the cross-section perpendicular to thedrive shaft (17) can be represented by a line along a reference straightline (68) passing through the center of the drive shaft (17).

The operative surface (52) on the cross-section perpendicular to thedrive shaft (17) can be represented as a line along reference curvedlines (54, 64) extending from the drive shaft (17), and a tangent line(56) at an arbitrary point on the reference curved lines (54, 64) can beinclined towards the rear of the rotational direction of the drive shaft(17) with respect to a straight line (57) passing through the arbitrarypoint and the center of the drive shaft (17).

The vanes (15, 63) in the above-noted configuration have a function ofsending the cake in a radial direction, and a function of generating afiltering force with respect to the cake. The filtering force withrespect to the cake is obtained as a force of repulsion with respect toa sliding resistance between the vanes (15, 63) and the side plate (1).

The reference curved line (64) can be can be a logarithmic spiral havingan intersecting angle (α) with the tangent line (56) and the straightline (57) that is constant and not dependent upon the position of thearbitrary point.

Because the intersection angle (α) is constant, the vane (63) in theabove-noted configuration, in proximity to the annular plate (12), wherethe water content of the cake is reduced, there is an increase in therotating wedge operating force and the force which moves the cake in aradial direction along a curved line, so that a large shear force isapplied to the cake.

The operative surface (52) in the cross-section can be represented by apiecewise linear curve (62) formed by a plurality of straight linesegments.

In the above-noted configuration, the vane (67) is easy to manufactureand provides sufficient strength.

The vanes (15, 63, 65, 67) can have a rear surface (53) to the rear inthe rotation direction of the drive shaft (17) and a rib (27) whichprotrudes from the rear surface (53) and reinforces the vane (15).

According to the above-noted configuration, the strength of the vanes(15, 63, 65, 67) is increased. For this reason, a rotating wedge actionis achieved with respect to the cake, which has a reduced water contentand increased sliding resistance.

A scraper (26) in proximity to the side plate (1) can be provided on atleast one side edge (15 a) of the vane (15).

According to the above-noted configuration, the thin film cake on thefilter element (4) with high filter resistance is scraped off, therebysuccessively renewing the filter elements (4). It is therefore possibleto perform continuous filtering operation over a long period of time.

A resin coating can be applied to the operative surface (52).

According to the above-noted configuration, the sliding resistance ofthe cake with respect to the operative surface (52) when the cake iscompressed during rotation is reduced. Therefore, in addition to anincrease in the operating efficiency of the apparatus, it becomesdifficult for the cake to rotate in concert with the vane (15).

The above-noted apparatus according to the first aspect can be providedwith valve mechanisms (8, 8 a) that increase and decrease the amount ofopening of the ejection port (7).

According to the above-noted configuration, the amount of opening of theejection port (7) is adjusted by the valve mechanisms (8, 8 a), so thatthe cake is subject to back pressure, dewatered under compression, andejected from the ejection port (7).

The valve mechanism (8) can have a pair of rotating shafts (28, 28)rotatably supported with respect to the opposing edge of the ejectionport (7), a pair of dampers (29, 29) fixed to each of the rotatingshafts (28) which open and close the ejection port (7), a cylinder (32)having a rod (33), and two links (30, 30) that link the rod (33) and therotating shafts (28, 28), convert the reciprocating motion of the rod(33) to rotational motion of the rotating shafts (28, 28) and transmitthis motion.

In the above-noted configuration, the amount of opening of the ejectionport is adjusted by a valve (8) having a simple construction. As aresult, back pressure is received, and compression dewatering is done,so that a cake having substantially uniform water content is ejectedfrom the center of the ejection port (7).

The valve mechanism (8 a) can have a rotating shaft (28 a) rotatablysupported with respect to the ejection port (7), a damper (29 a) fixedto the rotating, shaft (28 a) that opens and closes he ejection port(7), a cylinder (32) having a rod (33), and a lever (43) that links therod (33) and the rotating shaft (28 a), converts reciprocating motion ofthe rod (33) to rotational motion of the rotating shaft (28 a), andtransmits this motion.

In the above-noted configuration, the amount opening of the ejectionport (7) is adjusted by the valve mechanism (8 a) vz having a simpleconstruction. As a result, back pressure is received, and compressiondewatering is done, so that a cake having substantially uniform watercontent is ejected from the ejection port (7).

An apparatus according to the above-noted first aspect, a cleaningnozzle (34) can further be provided for the filter element (4). Thecleaning nozzle (34) can be disposed in opposition to the filter element(4) on the outside of the side plate (1).

According to the above-noted configuration, when operation of theapparatus is ended, cake remaining on the filter element (4) is removedwell by cleaning water discharged from the cleaning nozzle (34).

A plurality of the vane (15) in the above-noted first aspect can beprovided. By doing this, even for a raw fluid that is difficult tofilter, there is an increase in the shear force and the transportingforce acting one the cake, so that the cakes are pressurized andtransported with good balance, thereby achieving cakes having a lowwater content.

The side plates (1, 1) can be disposed so as to be substantially mutualparallel, with the distance (D) from an end edge (15 b) of one vane (15)to an adjacent vane (15) to the rear thereof with respect to thedirection of rotation established as being greater than the length (L)between the side plates (1, 1). By doing this, the filter surface areathat tries to stop the cake can be made more than twice the operativesurface (52) of the vane (15) that attempts to move the cake,effectively preventing the in-concert rotation of the cake.

A continuous compression-type dewatering apparatus according to a secondaspect of the present invention has a plurality of filter units (70)provided inparallel, and a drive shaft (17). Each filter unit (70) has afilter chamber (3) divided into to an annular plate (2) and two sideplates (1, 1), and a vane (15) disposed within the filter chamber (3).The annular plates (2, 2) are disposed about a common axis. The driveshaft (17), passes through the center axis of the annular plates (2, 2),and through the inside of the filter chambers (3, 3), and is freelyrotatably with respect to the filter chamber (3).

The vane (15) is fixed with respect to drive shaft (17), extends fromthe drive shaft (17) toward the annular plate (2), and rotates inconcert with the drive shaft (17). A supply path (50) that supplies rawfluid to the filter chamber (3) is formed inside the drive shaft (17).The vane (15) has two side edges (15 a) that face the side plates (1,1), and an end edge (15 b) that faces the annular plate (2). Of the sideplates (1, 1) of the filter unit (70), at least one side plate includesa filter element (4) for the purpose of separating the raw fluid into aliquid and a cake. The annular plate (2) includes an ejection port forthe cake. By the action of flow pressure of the raw fluid from thesupply path (50) to within the filter chamber (3) and the rotation ofthe vane (15), the filtered fluid flows out form the filter element (4)to the outside of the filter chamber (3), a cake that remains inside thefilter chamber (3) being pushed to the outside of the filter chamber (3)from the ejection port (7).

In the above-noted configuration, because a plurality of filter chambers(3) are provided in parallel, it is possible to perform simultaneousfiltering of a large quantity of raw fluid. Additionally, the amount ofspace occupied by the apparatus is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section view of a continuous compression-typedewatering apparatus according to an embodiment of the presentinvention.

FIG. 2 is a cross-section view along the line II—II of FIG. 1.

FIG. 3 is a cross-section view showing the filter chamber.

FIG. 4 is a plan view of the wedge wire screen of FIG. 1, viewed fromthe direction of arrow IV.

FIG. 5 is a cross-section view along the line V—V of FIG. 1.

FIG. 6 is a cross-section view showing another aspect of a filter plate.

FIG. 7 is partially enlarged view of FIG. 1.

FIG. 8 is a cross-section view of a vaned wheel.

FIG. 9 is a cross-section view showing the condition in which a scraperis mounted to a vaned wheel.

FIG. 10 is a front view of a vaned wheel.

FIG. 11 is a front view showing another aspect of a vaned wheel.

FIG. 12 is a front view showing yet another aspect of a vaned wheel.

FIG. 13 is a front view showing yet another aspect of a vaned wheel.

FIG. 14 is an enlarged view of FIG. 2 showing a back-pressure adjustmentvalve.

FIG. 15 is a cross-section view along the line XV—XV of FIG. 14.

FIG. 16 is a cross-section view along the line XVI—XVI of FIG. 14.

FIG. 17 is a cross-section view showing another aspect of aback-pressure adjustment valve.

FIG. 18 is a cross-section view along the line XVIII—XVIII of FIG. 17.

FIG. 19 is a cross-section view of a continuous compression-typedewatering apparatus according to another embodiment of the presentinvention.

BEST NODE FOR CARRYING OUT THE INVENTION

A preferred embodiment of the present invention is described below, withreference to drawings.

As shown in FIG. 1, a continuous compression-type dewatering apparatushas a filter chamber 3, a drive shaft 17, a vaned wheel 14, and a supplypath 50 for supplying raw fluid.

The filter chamber 3 is delineated by cylindrically shaped annular plate2, and a pair of side plates in the form of disc-shaped filter plates(hereinafter each respectively simply called “filter plates”) 1, 1substantially in mutually parallel opposition to each other, into acylindrical shape having a prescribed width L in the horizontaldirection.

As shown in FIG. 4 and FIG. 5, each filter plate 1, 1 is made up by asubstantially donut-shaped wedge wire screen (filter element) 4, anannular outer frame 5, an annular inner frame 6, and ribs 5 a, 5 b.Outer peripheral edge of the filter plates 1, 1 (the outer frame 5), isjoined and fixed to the both edges of the annular plate 2.

The screen 4 is made up of a plurality of wedge wires 4 a aligned in aplane at a prescribed spacing, and a plurality of support rods extendingin a direction substantially perpendicular to the wedge wires 4 a. Thesupport rod 4 b is joined to the wedge wire 4 a and supports the wedgewire 4 a. The spacing between the wedge wires 4 a forms fine holes.These fine holes exist in uniform density over substantially the entirearea of the filter plate 1. For this reason, it is difficult forfiltered liquid and solids to become clogged, thereby reducing thefrequency of cleaning the filter plate 1.

The size of the minute holes of the screen 4 (the distance betweenadjacent wedge wires) is set to a value at which there is little passageof sludge and at which ejection of filtered fluid is good, and also atwhich it is difficult for sludge to become clogged. In the case offiltering sludge that is difficult to filter, the size of the fine holesis preferably made no smaller than 50 μm and no larger than 300 μm.

In place of the wedge wire screen 4, it is possible to use a metalscreen formed by a punched metal, or a thin metal plate into which holeshave been formed by an electron beam.

The ribs 5 a extend in a radial direction of the outer frame 5 and linkthe outer frame 5 and the inner frame 6. The rib 5 b links between ribs5 a.

The screen 4 is fitted between the outer frame 5 and the inner frame 6,and is supported by the outer frame 5, the inner frame 6, and the ribs 5a and 5 b.

As shown in FIG. 6, at least one part of the annular plate 2 can be madeof the same type of screen (filter element) 9 as the screen 4 of thefilter plate 1. By doing this, the filter surface area is increased bythe amount of the screen that faces the filter chamber 3.

As shown in FIG. 1, both ends of the inner frame 6, are fixed andsupported by a pair of supporting tubes 10, 10 that are in mutualopposition. The supporting tubes 10 are supported on a frame 13.

The drive shaft 17 is cylindrical in shape, and passes through thecenter axis of the annular plate 2, and through the center of both thesupporting tubes 10, 10, and through the inside of the filter chamber 3.Both ends of the drive shaft 17 are rotatably supported via the bearings12, 12 to the supporting tubes 10, 10. That is, the drive shaft 17 canrotate freely with respect to the filter chamber 3.

As shown in FIG. 2 and FIG. 7, the vaned wheel 14 is formed by a boss 16and a plurality (6 in the embodiment shown in FIG. 2) of vanes 15. Theboss 16 is fitted into and fixed to the outer periphery of the driveshaft 17 between the supporting tubes 10, 10, and the vaned wheelrotates in concert with the drive shaft 17. The vane iSis disposedwithin the filter chamber 3, and extends outward toward the annularplate in a radial manner. Each vane 15 has two side edges 15 a, 15 athat face the filter plates 1, 1 and an end edge 15 b that face theannular plate 2.

The supply path 50 is formed by a main supply path 18, a supply port 19,and a linking path 11. The main supply path 18 passes through the insideof the drive shaft 17. The supply port 19 is formed in the drive shaft17 on both sides of the boss 16 and opens toward the main supply path18. The linking path is adjacent to the drive shaft 17 and is delineatedby the drive shaft 17, the supporting tubes 10 and the inner frame 6.The linking path 11 links the supply port 19 and the filter chamber 3.

As shown in FIG. 1, one end of the drive shaft 17 is connected to asludge tank 22, via a free joint 20, a supply pipe 21, and a supply pump23. The other end of the drive shaft 17 is connected to a back flow pipe44 via a free joint 51.

Raw fluid (sludge) in the sludge tank 22 is sent into the main supplypath 18 by the supply pump 23. As shown in FIG. 7, raw fluid in the mainsupply path 18 passes through the supply port 19 and the linking path11, and flows into the filter chamber 3. The supply pressure into thefilter chamber 3 by the supply pump is set to a value, for example, inthe range from 0.1 kg/cm² to 0.7 kg/cm².

The raw fluid that has flowed into the filter chamber 3 is subjected tothe pressure from the supply pump and the action of the rotation of thevane 15, so that it moves toward the annular plate 2. When this occurs,water content (filtered fluid) passes through the two filter plates 1,1, and is ejected from the inside of the filter chamber 3, the cakeremaining in the filter chamber 3 being subjected to pressure from theoperative surface 52 of the vane 15, to be described later, so that itmoves toward the annular plate 2 as it is compressed. In the process ofbeing compressed, water content is successively ejected from the filterplate 1. In proximity to the annular plate 2, the water content of thecake is minimum.

As shown in FIG. 7, the side edge 15 a of the vane 15 is in proximity tothe screen 4. By the action of the side edge 15 a of the rotating vane15, a cake on the inside surface of the screen 4 is scraped away, sothat the screen 4 is constantly being renewed. The side edge 15 a canalso be disposed so as to be in contact with the screen 4.

As shown in FIG. 9, it is possible to provide a rubber or resin scraper26 on the side edge 15 a of the vane, for the purpose of scraping offthe cake. By doing this, it is possible to better remove the cake fromthe screen 4. The scraper 26 can also be disposed so as to be in contactwith the screen 4.

As shown in FIG. 10, each vane 15 is a curved plate having asubstantially uniform thickness, and having an operative surface 52 onthe side toward the direction of rotation and a rear surface 53 to therear of the direction of rotation. The operative surface 52 viewed incross-section with a cutting plane perpendicular to the drive shaft 17can be represented by a reference curved line 54 extending from thedrive shaft 17. The shape of the line of the operative surface 52 incross-section with a cutting plane perpendicular to the drive shaft 17is not dependent upon the position of the cutting plane in the axialdirection of the drive shaft 17, and is substantially uniform. A tangentline at an arbitrary point on the reference curved line 54 is inclinedin the rearward direction with respect to the direction of a straightline 57 passing through the arbitrary point and the center of the driveshaft 17.

A vane 15 shaped as noted above has a function of sending a cake in aradial direction, and a function of generating a filtering force withrespect to the cake. The filtering force with respect to the cake isobtained as a force of repulsion with respect to a sliding resistancebetween the vane 15 and the filter plate 1 (screen 4).

If the angle α of intersection (lag angle) between the tangent line 56and the straight line 57 is small, the sliding resistance of the cakewith respect to the operative surface 52 becomes larger than the slidingresistance of the cake with respect to the screen 4, making it easierfor the cake to rotate in concert with the vane 15. If, however, the lagangle α is large, the spacing between adjacent vanes 15 becomes small,and becomes easy for the cake to rotate in concert. In order toeffectively limit the cake from rotating with the vane and to achievethe effect of moving the cake, it is preferable that the lag angle α bemade at least 200 and no greater than 50°, and more preferable that itbe made at least 300 and no greater than 45°.

The number of vanes 15 is best made large, so as to generate a filteringforce. However, as the number of vanes increases, because of the narrowspacing between the vanes 15, it becomes easy for the cake to rotate inconcert, thereby sacrificing the function of sending the cake.Therefore, the number of vanes 15 is established so as to achieve bothgood sending of the cakes and effective generation of a filtering force.Specifically, for a lag angle α set to a prescribed value, the number ofvanes 15 should be set to a number for which the distance D from an endedge 15 a of one vane 15 to the operative surface 52 of another,adjacent vane 15 to the rear thereof with respect to the rotationaldirection, is greater than the width L of the filter chamber 3 (distancebetween filter plates 1, 1) shown in FIG. 3.

As shown in FIG. 8 and FIG. 10, a reinforcing plate 27 for reinforcingthe vane 15 is fixed to the rear surface 53 of each vane 15, along thecenter line of the vane 15. The reinforcing plate 27 is disposedsubstantially parallel to the screen 4 (refer to FIG. 1), and protrudesfrom the rear surface 53. The amount of protrusion of the reinforcingplate 27 from the rear surface 53 should be large in order to reinforcethe vane 15, and should be small in order to limit the rotation inconcert of the cake attributed to the reinforcing plate 27. In order toboth provide good reinforcement of the vane 15 and minimization ofrotation in concert of the cake, the height of the protrusion of thereinforcing plate 27 from the rear surface 53 is set so as to graduallybe reduced from the boss 16 towards the end edge 15 b.

On the operative surface 52 a coating made of a material havinglubricating qualities and resistance to wear, such as Teflon™, Nylon™,or a high polymer resin can be applied. By doing this, the slidingresistance of the cake with respect to the operative surface 52 isreduced, making it easier to transport the cake.

FIG. 11 to FIG. 13 show examples of vaned wheels 58, 59, and 60 in placeof the vaned wheel 14.

A vane 63 of the vaned wheel 58 of FIG. 11 differs from the vane 15 ofFIG. 10 in its lag angle α and the number of vanes. The reference curvedline 64 of the vane 63 is made a logarithmic spiral curve, and thenumber of vanes 63 is 4. A logarithmic spiral curve is one in which thelag angle α and the wedge angle β are constant, regardless of theposition on the curve. The wedge angle β is the angle of intersectionbetween the normal line 61 and the tangent line 56, the sum of the lagangle α and the wedge angle β making a right angle. By keeping the lagangle a constant, the rotating wedge force of the vane 63 and the forcethat acts to move the cake in the radial direction in proximity to theannular plate 2, at which the water content of the cake is loweredincrease, thereby applying a large shear force to the cake. In the samemanner as the vane 15 of FIG. 10, the distance D from an end edge of onevane 63 to the operative surface 52 of another, adjacent vane 63 to therear with respect to the direction of rotation is larger than the widthL of the filter chamber 3.

A vane 65 of the vaned wheel 59 of FIG. 12 is different from the vane 15of FIG. 10, in that the operative surface 52 thereof has a piecewiselinear curve 62 having a plurality (four) line segments 62 a, 62 b, 62c, and 62 d that approximate a reference curve 66. The reference curve66 is a logarithmic spiral curve having a lag angle of 35°. With a vane59 such as this, because there is no need for form the vane 65 into acurve, manufacturing is facilitated, and strength is increased. Althoughthe number of line segments in the piecewise linear curve 62 is notparticularly restricted, it should be at least two but no greater thanten.

A vane 67 of the vaned wheel 60 of FIG. 13 is different from the vane 15of FIG. 10 in that the operative surface 52 cross-section is representedby a line along a reference straight line 68 passing through the centerof the drive shaft 17. Depending upon the properties of the raw fluid(sludge) to be filtered, it is possible to use this type of flat platevane 67 as well. If the operative surface 52 is substantially parallelto the reference straight line 68, condition in which there issubstantial coincidence with the reference straight line 68 is included.

In the vaned wheels 58, 59, and 60 of FIG. 11 to FIG. 13 as well,similar to the vaned wheel 14 of FIG. 10, the vanes 63, 65, and 67 havetwo side edges facing the filter plates 1, 1 and an end edge facing theannular plate 2. Each of the vanes He 63, 65, and 67 is made of a platehaving a substantially uniform thickness, and has an operative surface52 in the forward direction of rotation and a rear surface 53 to therear with respect to the direction of rotation. The shape of the line ofthe operative surface 52 in cross-section with a cutting planeperpendicular to the drive shaft 17 is not dependent upon the positionof the cutting plane in the axial direction of the drive shaft 17, andis substantially uniform. A reinforcing plate 27 is fixed to the rearsurface of each of the vanes 63, 65, and 67.

As shown in FIG. 1 and FIG. 2, a pulley 25 is fitted into and fixed tothe outer periphery of one end of the drive shaft 17. This pulley 25 islinked to a drive pulley 24 a of a drive apparatus 24 by a belt 69. The;rotational drive force of the drive apparatus 24 is transmitted to thedrive shaft 17 via the pulley 24 a, the belt 69, and the pulley 25, sothat the vaned wheel 14 within the filter chamber. 3 rotates in concertwith the drive shaft 17.

The supply pump 23 pumps raw fluid from the main supply path 18 insidethe drive shaft 17 into the filter chamber 3 at a pressure of, forexample, 0.1 to 0.7 kg/cm². The raw fluid inside the filter chamber 3 isfirst pressed against the filter plates 1, ion both sides by this inflowpressure, and is filtered. The drive apparatus 24 causes the vaned wheel14 to rotate at a circumferential speed of, for example, 100 to 500mm/minute. The raw fluid inside the filter chamber 3 is transportedtoward the annular plate 2 as it is compressed by the operative surface52 of the rotating vane 15. When this occurs, the filtered fluid issuccessively ejected from the filter plate 1. As a result, in asubstantially triangular space formed between the operative surface 52of the vane 15 and the annular plate 2, water content is removed fromthe raw fluid and a compressed cake collects.

As shown in FIG. 2, on the bottom of the annular plate 2, asubstantially rectangular ejection port 7 is formed for the purpose ofejecting a cake inside the filter chamber 3. A back-pressure adjustmentvalve (valve mechanism) 8 that increasing and decreases the openingamount of the ejection port 7 is provided on this ejection port 7.Downstream from the back-pressure adjustment valve 8 is disposed cakechute 41.

Because of the need to remove a cake beforehand when the apparatus is tobe stopped for a long period of time, the ejection port 7 is preferablydisposed on the lower half peripheral region of the annular plate 2. Toprevent contact between a cake that is ejected from the ejection port 7and filtered fluid ejected from the filter plate 1, it is preferablethat the ejection port 7 be disposed at a position on the annular plate2 that is inclined at substantially 45° from vertical.

As shown in FIG. 14, FIG. 15, and FIG. 16, the back-pressure adjustmentvalve 8 has a pair of rotating shafts 28, 28 rotatably supported withrespect to the opposing edge of the ejection port 7, a pair of dampers29, 29 fixed to each of the rotating shafts 28 which open and close theejection port 7, a cylinder 32 having a rod 33, and two links 30, 30that link the rod 33 and the rotating shafts 28, 28, convert thereciprocating motion of the rod 33 to rotational motion of the rotatingshafts 28, 28 and transmit this motion. As shown in FIG. 15, a fixinghole 30 a, into which the rotating shaft 28 is passed and fixed, isformed on one end of each of the links 30. On the other end of each ofthe links 30 is formed an elongated hole 31, these holes being mutuallysuperposed. The shaft 33 a that is fixed to the rod 33 is rotatablypassed through the elongated holes 31. By doing this, when the rod 33extends, the dampers 29, 29 rotate so as to approach one another (theclosing direction), and when the rod 33 retracts, the dampers 29, 29rotate so as to retract from one another (the opening direction).Because of the rotational frictional force of the vaned wheel 14 and thestopping down of the ejection port 7, back pressure is developed withinthe filter chamber 3. By the application of back pressure to the cake,the cakes are continuously compressed and dewatered, and ejected fromthe ejection port 7.

FIG. 17 and FIG. 18 show another example of a back-pressure adjustmentvalve 8 a. The back-pressure adjustment valve 8 a has a rotating shaft28 a rotatably supported with respect to an edge of a member 7 a forminga lower edge of the ejection port 7, a damper 29 a fixed to the rotatingshaft 28 a and which opens and closes the ejection port 7, a cylinder 32having a rod 33, a lever 43 linking the rod 33 and the rotating shaft 28a, which converts the reciprocating motion of the rod 33 to rotationalmotion of the rotating shaft 28 a and transmits this motion. One end ofthe lever 43 is fixed to the rotating shaft 28 a, and the other end ofthe lever 43 is rotatably linked to the rod 33. The lever 43 isconfigured so to freely expand and contract itself. When the rod 33expands, the damper 29 a rotates in the opening direction, and when therod 33 contracts, the damper 29 a rotates in the closing direction.

The back-pressure adjustment valves 8, 8 a can also have a means fordetecting the pressure within the filter chamber 3. Specifically, asensor for detecting the pressure within the filter chamber 3 can befixed to an inside surface of the annular plate 2. If the opening of theejection port 7 is adjusted in response to the detected value from thesensor (pressure within the filter chamber 3), it is possible to adjustthe water content of the cake ejected from the ejection ports 7, 7 a soas to be more uniform. It is also possible to provide a control circuitfor controlling the cylinder 32 in response to the detected value fromthe sensor.

As shown in FIG. 1 and FIG. 2, cleaning nozzles 34 for cleaning thescreen 4 is disposed on the outside of the filter plates 1, 1 above thedrive shaft 17. Each cleaning nozzle 34 is fixed to a cleaning waterpipe 35. The end part of the cleaning water pipe 35 is linked to acleaning water supply pipe via a swivel joint 36. A pulley 38 is fixedto the outer periphery at the end part of the cleaning water pipe 35,this pulley 38 being linked to a drive apparatus 39. The drive apparatus39 causes the cleaning water pipe 35 to undulate via the pulley 38. Bydoing this, the cleaning nozzles 34 reciprocally move over the outersurface of the filter plates 1, 1, so as to spray cleaning water ontothe screen 4.

The filter chamber 3 at the top of the drive shaft 17 (filter plates 1,1 and annular plate 2) and the cleaning nozzles 34 are covered by acover 42 to prevent spraying of the cleaning water. The end part of thecleaning water pipe 35 is passed through the cover 42. The filterchamber 3 at the bottom of the drive shaft 17 (filter plates 1, 1 andannular plate 2) is covered by a trough 40 for receiving filtered fluid.Filtered fluid ejected from the screen 4 flows out of an ejection port40 a formed in the bottom part of the trough 40.

A method of using an apparatus configured as described above is asfollows.

At start of use, when the filter chamber 3 is empty, the vaned wheel 14is caused to rotate at a very low speed with the ejection port 7 closed,as raw fluid (sludge) is supplied to the filter chamber 3. When this isdone, the rotational speed of the vaned wheel is set in the range, forexample, from 100 to 500 mm/minute, and the raw fluid supply pressure isset in the range, for example, of 0.1 to 0.7 kg/cm². Raw fluid that hasflowed into the filter chamber 3 receives the above-noted supplypressure and the pressure from the operative surface 52 of the vane 15and is transported under pressure in the direction of the outerperiphery. When this occurs, the screens 4, 4 of the filter plates 1, 1successively filter the raw fluid. Concentration of raw fluidimmediately after it flows into the filter chamber 3 is mainly done bythe above-noted supply pressure. The vaned wheel 14 presses on the rawfluid with a force that exceeds the sliding friction force between theconcentrated raw fluid and the filter plates 1, 1, so that the raw fluidis pushed outward in the radial direction as it is dewatered, by thesupply pressure and the rotating wedge force of the vane 15 having a lagangle of α. As a result, the raw fluid is turned into a cake, as thecake, moving along a curved line, is subjected to a shear force.

After the elapse of a prescribed amount of time, when the filter chamber3 is filled with a cake and the pressure therein rises, the ejectionport 7 is opened by a prescribed amount. By doing this, the compressedcake receives back pressure from the ejection port 7 and is ejected.With the pressure in the filter chamber 3 adjusted, cakes of a desiredwater content are continuously ejected.

By providing a scraper 26 in contact with the screen 4 at the edge ofthe vane 15, it is possible to reliably prevent the occurrence ofclogging of the screen 4, making continuous operation possible.

When operation is ended, cleaning water discharged from the cleaningnozzle 34 cleans the raw fluid (sludge) attached to the filter plates 1,1, whereupon the apparatus is stopped.

Another embodiment of the present invention is described below.

FIG. 19 shows a continuous compression-type dewatering apparatus havinga plurality of filter chambers 3 arranged in parallel. Parts of thisapparatus that are the same as those in FIG. 1 are assigned the samereference symbols, and will not be described herein.

The apparatus of FIG. 19 has a plurality of filter units 70 provided inparallel, and a drive shaft 17. Each filter unit 70 has a filter chamber3 delineated by an annular plate 2 and two filter plates 1, 1, and avaned wheel 14 disposed inside the filter chamber 3.

The plurality of annular plates 2 are disposed about a common centeraxis. The drive shaft 17 passes through the annular plates 2 and throughthe inside of the filter chambers 3, and is freely rotatable withrespect to the filter chambers 3. The drive shaft 17 is supported on aframe 13 by supporting tubes 10, 10 a, and 10 b.

The vaned wheel 14 is fixed to the drive shaft 17 and rotates in concertwith the drive shaft 17. Inside the drive shaft 17 is formed a mainsupply path 18 which supplies raw fluid to each of the filter chambers3. Each vane 15 of the vaned wheels 14 has two side edges facing thefilter plates 1, 1, and an end edge facing the annular plate 2.

Each of the filter plates 1 includes a screen for separating the rawfluid into filtered fluid and a cake. The annular plate 2 includes anejection port for the cake. The screen and the ejection port areconfigured the same as shown in FIG. 2.

The inflow pressure of the raw fluid from the main supply path 18 intothe filter chamber 3 and the rotation of the vane 15 causes the filteredfluid to flow to the outside of the filter chamber 3 from the screen 4,a cake remaining inside the filter chamber 3 being pushed to the outsideof the filter chamber 3 from the ejection port 7.

According to an apparatus configured in this manner, by a plurality offilter chambers 3, it is possible to simultaneously process a largeamount of sludge. Because the placement is that of the filter chambers 3being aligned in a row, the space occupied by the apparatus is reduced.

IN INDUSTRIAL APPLICABILITY

As described above, a continuous compression-type dewatering apparatusaccording to the present invention is useful in continuouscompression-type dewatering of concentrated sludge, and is particularlysuited to continuous compression-type dewatering of difficult-to-filtersludge, such as sewage sludge.

What is claimed is:
 1. A continuous compression-type dewatering apparatus comprising: a filter chamber (3) delineated by an annular plate (2) and two side plates (1,1); a drive shaft (17) passing through a center axis of the annular plate (2), passing through the inside of the filter chamber (3), and freely rotatable with respect to the filter chamber (3); a vane (15) disposed within the filter chamber (3), fixed with respect to the drive shaft (17), extending from the drive shaft (17) toward the annular plate (2), and rotating in concert with the drive shaft (17); and a supply path (50) passing through the drive shaft (17), supplying raw fluid to the filter chamber (3), wherein the vane (15) comprises two side edges (15 a, 15 a) facing the side plates (1,1) and an end edge (I5 b) facing the annular plate (2), at least one of the side plates (1,1) including a filter element (4) for separating the raw fluid into a filtered fluid and a cake, the annular plate (2) includes an ejection port (7) for the cake, the ejection port is provided with a valve mechanism (8) which increases and decreases an amount of opening of the ejection port (7), the valve mechanism (8) comprises a pair of rotating shafts (28, 28) rotatably supported with respect to an opposing edge of the ejection port (7), a pair of dampers (29, 29) fixed to each of the rotating shafts (28) which open and close the ejection port (7), a cylinder (32) having a rod (33), and two links (30, 30) that link the rod (33) and the rotating shafts (28, 28), convert reciprocating motion of the rod (33) to rotational motion of the rotating shafts (28, 28), and transmit this motion, and an inflow pressure of the raw fluid from the supply path (50) into the filter chamber (3) and rotation of the vane (50) causes the filtered fluid to flow out from the filter element (4) to the outside of the filter chamber (3), a cake that remains inside the filter chamber (3) being pushed to the outside of the filter chamber (3) via the ejection port (7).
 2. A continuous compression-type dewatering apparatus according to claim 1, wherein the filter element (4) is disposed over substantially the entire region of the side plate (1).
 3. A continuous compression-type dewatering apparatus according to claim 2, wherein the filter element (4) is a substantially donut-shaped screen having a large number of fine holes.
 4. A continuous compression-type dewatering apparatus according to claim 3, wherein the side plate (1) comprises the screen (4), an annular outer frame (5) fixed to an outer periphery of the screen (4), an annular inner frame (6) fixed to an inner periphery of the screen (4), and a rib (5 a) linking the outer frame (5) and the inner frame (6).
 5. A continuous compression-type dewatering apparatus according to claim 1, wherein the annular plate (2) has, on an inner circumference thereof, a second filter element (9) for separating the raw fluid into the filtered fluid and the cake.
 6. A continuous compression-type dewatering apparatus according to claim 5, wherein the second filter element (9) is a screen (9) having a large number of fine holes.
 7. A continuous compression-type dewatering apparatus according to claim 1, wherein the vane (15) comprises an operative surface (52) in the forward direction with respect to the direction of rotation of the drive shaft (17), the operative surface (52) in cross-section with a cutting plane perpendicular to the drive shaft (17) is represented by a reference curved line (54, 64) extending from the drive shaft (17), and a line tangent to an arbitrary point on the reference curved line (54, 64) is inclined towards the rear of the rotational direction of the drive shaft (17) with respect to a straight line (57) passing through the arbitrary point and the center of the drive shaft (17).
 8. A continuous compression-type dewatering apparatus according to claim 7, wherein the reference curved line (64) is a logarithmic spiral curve having an angle of intersection (a) between the tangent line (56) and the straight line (57) that is constant and not dependent upon the position of the arbitrary point.
 9. A continuous compression-type dewatering apparatus according to claim 7, wherein the operative surface on the cross-section is a piecewise linear curve (62) having a plurality of straight line segments approximating the reference curved line to be the logarithmic spiral curve (66).
 10. A continuous compression-type dewatering apparatus according to claim 1, further comprising a cleaning nozzle (34) disposed on an outside of the side plate (1) for cleaning the filter element (4).
 11. A continuous compression-type dewatering apparatus according to claim 10, wherein the cleaning nozzle (3-4) is disposed so as to oppose the filter element (4) on the outside of the side plate (1).
 12. A continuous compression-type dewatering apparatus according to claim 1, wherein the filter element (4) is, provided on each side plate (1).
 13. A continuous compression-type dewatering apparatus according to claim 1, wherein the supply path (50) comprises a main supply path (18) inside the drive shaft (17), a supply port (19) formed in the drive shaft (17) and opening the main supply path (18), and a linking path (11) adjacent to drive shaft (17) on the side of the vane (15), linking the supply port (19) and the filter chamber (3), and the raw fluid flows from the main supply path (18), via the supply port (19) and linking path (11), into the filter chamber (3).
 14. A continous compression-type dewatering apparatus according to claim 1, wherein the vane (15) comprises operative surface (52) in the forward direction with respect to the direction of rotation of the drive shaft (17), and the shape of the line of the operative surface in cross-section with a cutting plane perpendicular to the drive shaft (17) is not dependent upon the position of the cutting plane in the axial direction of the drive shaft (17), and is substantially uniform.
 15. A continuous compression-type dewatering apparatus according to claim 1, wherein the vane (15) comprises an operative surface (52) in the forward direction with respect to the direction of rotation of the drive shaft (17), and the operative surface (52) in cross-section with a cutting plane perpendicular to the drive shaft (17) is represented by a line along a reference straight line (68) passing through the center of the drive shaft (17).
 16. A continuous compression-type dewatering apparatus according to claim 1, wherein the vane (15) has a rear surface to the rear with respect to the direction of rotation of the drive shaft (17), and a reinforcing rib (27) reinforcing the vane (15) and protruding from the rear surface (53).
 17. A continuous compression-type dewatering apparatus according to claim 1, wherein a scraper (26) is provided on at least one side edge (15 a) of the vane (15), in proximity to the side plate (1).
 18. A continuous compression-type dewatering apparatus according to claim 1, wherein the vane (15) has an operative surface (52) in the forward direction with respect to the direction of rotation of the drive shaft (17), and a coating of resin on the operative surface (52), wherein the operative surface (52) of the vane sends a cake in a radial direction and generates a filtering force with respect to the cake, the filtering force is obtained as a force of repulsion with respect to a sliding resistance between the vane (15) and the side plate (1).
 19. A continuous compression-type dewatering apparatus comprising: a filter chamber (3) delineated by an annular plate (2) and two side plates (1, 1); a drive shaft (17) passing through a center axis of the annular plate (2), passing through the inside of the filter chamber (3), and freely rotatable with respect to the filter chamber (3); a plurality of vanes (15, 15) disposed within the filter chamber (3), fixed with respect to the drive shaft (17), extending from the drive shaft (17) toward the annular plate (2), and rotating in concert with the drive shaft (17); and a supply path (50) passing through the drive shaft (17), supplying raw fluid to the filter chamber (3), wherein each vane (15) comprises two side edges (15 a) facing the side plates (1, 1) and an end edge (I 5 b) facing the annular plate (2), at least one of the side plates (1, 1) includes a filter element (4) for separating the raw fluid into a filtered fluid and a cake, the annular plate (2) includes an ejection port (7) for the cake, the ejection port is provided with a valve mechanism (8) which increases and decreases an amount of opening of the ejection port (7), the valve mechanism (8) comprises a pair of rotating shafts (28, 28) rotatably supported with respect to an opposing edge of the ejection port (7), a pair of dampers (29, 29) fixed to each of the rotating shafts (28) which open and close the ejection port (7), a cylinder (32) having a rod (33), and two links (30, 30) that link the rod (33) and the rotating shafts (28, 28), convert reciprocating motion of the rod (33) to rotational motion of the rotating shafts (28, 28), and transmit this motion, and an inflow pressure of the raw fluid from the supply path (50) into the filter chamber (3) and rotation of the vanes (15, 15) causes the filtered fluid to flow out from the filter element (4) to the outside of the filter chamber (3), a cake that remains inside the filter chamber (3) being pushed to the outside of the filter chamber (3) via the ejection port (7).
 20. A continous compression-type dewatering apparatus according to claim 19, wherein the side plates (1, 1) are disposed so as to be substantially mutually parallel, with a distance (D) from an end edge (15 b) of one vane (15) to an adjacent vane (15) to the rear thereof with respect to the direction of rotation established as being greater than a length (L) between the side plates (1, 1).
 21. A continuous compression-type dewatering apparatus comprising: a plurality of filter units (70) provided in parallel; and a drive shaft (17), wherein each filter unit (70) comprises a filter chamber delineated by an annular plate (2) and two side plates (1, 1) and a vane (15) disposed within the filter chamber (3), the annular plates (2, 2) are disposed around a common center axis and the drive shaft (17) passes through the center axis of the annular plates (2, 2) and through the inside of the filter chambers (3), and is free to rotate with respect to the filter chambers (3), the vane (15) is fixed with respect to the drive shaft (17), extends in a radial direction towards the annular plate (2), and rotates in concert with the drive shaft (17), a supply path (50) supplying raw fluid to each filter chamber (3) is formed inside the drive shaft (17), the vane (15) has two side edges (15 a) facing the side plates (1, 1), and an end edge (15 b) facing the annular plate (2), at least one of the side plates (1, 1) of each filter unit (70) includes a filter element (4) for separating the raw fluid into a filtered fluid and a cake, the annular plate (2) includes an ejection port (7) for the cake, the ejection port is provided with a valve mechanism (8) which increases and decreases an amount of opening of the ejection port (7), the valve mechanism (8) comprises a pair of rotating shafts (28, 28) rotatably supported with respect to an opposing edge of the ejection port (7), a pair of dampers (29, 29) fixed to each of the rotating shafts (28) which open and close with the ejection port (7), a cylinder (32) having a rod (33), and two links (30, 30) that link the rod (33) and the rotating shafts (28, 28), convert reciprocating motion of the rod (33) to rotational motion of the rotating shafts (28, 28), and transmit this motion, and an inflow pressure of the raw fluid from the supply path (50) into the filter chamber (3) and rotation of the vane (15) causes the filtered fluid to flow out from the filter element (4) to the outside of the filter chamber (3), a cake that remains inside the filter chamber (3) being pushed to the outside of the filter chamber (3) via the ejection port (7).
 22. A continuous compression-type dewatering comprising: a filter chamber (3) delineated by an annular plate (2) and two side plates (1, 1); a drive shaft (17) passing through a center axis of the annular plate (2), passing through the inside of the filter chamber (3), and freely rotatable with respect to the filter chamber (3); a vane (15) disposed within the filter chamber (3), fixed with respect to the drive shaft (17), extending from the drive shaft (17) toward the annular plate (2), and rotating in concert with the drive shaft (17); and a supply path (50) passing through the drive shaft (17), supplying raw fluid to the filter chamber (3), wherein the vane (15) comprises two side edges (15 a, 15 a) facing the side plates (1, 1) and an end edge (1 5 b) facing the annular plate (2), at least one of the side plates (1, 1) including a filter element (4) for separating the raw fluid into a filtered fluid and a cake, the annular plate (2) includes an ejection port (7) for the cake, the ejection port is provided with a valve mechanism (8 a) which increases and decreases an amount of opening of the ejection port (7), the valve mechanism (8 a) comprises a rotating shaft (28 a) rotatably supported with respect to the ejection port (7), a damper (29 a) fixed to the rotating shaft (28 a) that opens and closes the ejection port (7), a cylinder (32) having a rod (33), and a lever (43) that links the rod (33) and the rotating shaft (28 a), converts reciprocating motion of the rod (33) to rotational motion of the rotating shaft (28 a), and transmits this motion, and an inflow pressure of the raw fluid from the supply path (50) into the filter chamber (3) and rotation of the vane (50) causes the filtered fluid to flow out from the filter element (4) to the outside of the filter chamber (3), a cake that remains inside the filter chamber (3) being pushed to the outside of the filter chamber (3) via the ejection port (7).
 23. A continuous compression-type dewatering apparatus according to claim 22, wherein the filter element (4) is disposed over substantially the entire region of the side plate (1).
 24. A continuous compression-type dewatering apparatus according to claim 23, wherein the filter element (4) is a substantially donut-shaped screen having a large number of fine holes.
 25. A continuous compression-type dewatering apparatus according to claim 24, wherein the side plate (1) comprises the screen (4), an annular outer frame (5) fixed to an outer periphery of the screen (4), an annular inner frame (6) fixed to an inner periphery of the screen (4), and a rib (5 a) linking the outer frame (5) and the inner frame (6).
 26. A continuous compression-type dewatering apparatus according to claim 22, wherein the annular plate (2) has, on an inner circumference thereof, a second filter element (9) for separating the raw fluid into the filtered fluid and the cake.
 27. A continuous compression-type dewatering apparatus according to claim 26, wherein the second filter element (9) is a screen (9) having a large number of fine holes.
 28. A continuous compression-type dewatering apparatus according to claim 22, wherein the vane (15) comprises an operative surface (52) in the forward direction with respect to the direction of rotation of the drive shaft (17), the operative surface (52) in cross-section with a cutting plane perpendicular to the drive shaft (17) is represented by a reference curved line (54, 64) extending from the drive shaft (17), and a line tangent to an arbitrary point on the reference curved line (54, 64) is inclined towards the rear of the rotational direction of the drive shaft (17) with respect to a straight line (57) passing through the arbitrary point and the center of the drive shaft (17).
 29. A continuous compression-type dewatering apparatus according to claim 28, wherein the reference curved line (64) is a logarithmic spiral curve having an angle of intersection (α) between the tangent line (56) and the straight line (57) that is constant and not dependent upon the position of the arbitrary point.
 30. A continuous compression-type dewatering apparatus according to claim 28, wherein the operative surface on the above-noted cross-section is a piecewise linear curve (62) having a plurality of straight line segments approximating the reference curved line to be the logarithmic spiral curve (66).
 31. A continuous compression-type dewatering apparatus according to claim 22, further comprising a cleaning nozzle (34) disposed on an outside of the side plate (1) for cleaning the filter element (4).
 32. A continuous compression-type dewatering apparatus according to claim 31, wherein the cleaning nozzle (34) is disposed so as to oppose the filter element (4) on the outside of the side plate (1).
 33. A continuous compression-type dewatering apparating according to claim 23, wherein the filter element (4) is provided on each side plate (1).
 34. A continuous compression-type dewatering apparatus according to claim 22, wherein the supply path (50) comprises a main supply path (18) inside the drive shaft (17), a supply port (19) formed in the drive shaft (17) and opening the main supply path (18), and a linking path (11) adjacent to drive shaft (17) on the side of the vane (15), linking the supply port (19) and the filter chamber (3), and the raw fluid flows from the main supply path (18), via the supply port (19) and linking path ( 1I), into the filter chamber (3).
 35. A continuous compression-type dewatering apparatus according to claim 22, wherein the vane (15) comprises an operative surface (52) in the forward direction with respect to the direction of rotation of the drive shaft (17), and the shape of the line of the operative surface in cross-section with a cutting plane perpendicular to the drive shaft (17) is not dependent upon the position of the cutting plane in the axial direction of the drive shaft (17), and is substantially uniform.
 36. A continuous compression-type dewatering apparatus according to claim 22, wherein the vane (15) comprises an operative surface (52) in the forward direction with respect to the direction of rotation of the drive shaft (17), and the operative surface (52) in cross-section with a cutting plane perpendicular to the drive shaft (17) is represented by a line along a reference straight line (68) passing through the center of the drive shaft (17).
 37. A continuous compression-type dewatering apparatus according to claim 22, wherein the vane (15) has a rear surface to the rear with respect to the direction of rotation of the drive shaft (17), and a reinforcing rib (27) reinforcing the vane (15) and protruding from the rear surface (53).
 38. A continuous compression-type dewatering apparatus according to claim 22, wherein a scraper (26) is provided on at least one side edge (15 a) of the vane (15), in proximity to the side plate (1).
 39. A continuous compression-type dewatering apparatus according to claim 22, wherein the vane (15) has an operative surface (52) in the forward direction with respect to the direction of rotation of the drive shaft (17), and a coating of resin on the operative surface (52), wherein the operative surface (52) of the vane sends a cake in a radial direction and generates a filtering force with respect to the cake, the filtering force is obtained as a force of repulsion with respect to a sliding resistance between the vane (15) and the side plate (1).
 40. A continuous compression-type dewatering apparatus comprising: a filter chamber (3) delineated by an annular plate (2) and two side plates (1, 1); a drive shaft (17) passing through a center axis of the annular plate (2), passing through the inside of the filter chamber (3), and freely rotatable with respect to the filter chamber (3); a plurality of vanes (15, 15) disposed within the filter chamber (3), fixed with respect to the drive shaft (17), extending from the drive shaft (17) toward the annular plate (2), and rotating in concert with the drive shaft (17); and a supply path (50) passing through the drive shaft (17), supplying raw fluid to the filter chamber (3), wherein each vane (15) comprising two side edges (15 a) facing the side plates (1, 1) and an end edge (15 b) facing the annular plate (2), at least one of the side plates (1, 1) includes a filter element (4) for separating the raw fluid into a filtered fluid and a cake, the annular plate (2) includes an ejection port (7) for the cake, the ejection port is provided with a valve mechanism (8 a) which increases and decreases an amount of opening of the ejection port (7), the valve mechanism (8 a) comprises a rotating shaft (28 a) rotatably supported with respect to the ejection port (7), a damper (29 a) fixed to the rotating shaft (28 a) that opens and closes the ejection port (7), a cylinder (32) having a rod (33), and a lever (43) that links the rod (33) and the rotating shaft (28 a), converts reciprocating motion of the rod (33) to rotational motion of the rotating shaft (28 a), and transmits this motion, and an inflow pressure of the raw fluid from the supply path (50) into the filter chamber (3) and rotation of the vanes (15, 15) causes the filtered fluid to flow out from the filter element (4) to the outside of the filter chamber (3), a cake that remains inside the filter chamber (3) being pushed to the outside of the filter chamber (3) via the ejection port (7).
 41. A continuous compression-type dewatering apparatus according to claim 40, wherein the side plates (1, 1) are disposed so as to be substantially mutually parallel, with a distance (D) from an end edge (15 b) of one vane (15) to an adjacent vane (15) to the rear thereof with respect to the direction of rotation established as being greater than a length (L) between the side plates (1, 1).
 42. A continuous compression-type dewatering apparatus comprising: a plurality of filter units (70) provided in parallel; and a drive shaft (17), wherein each filter unit (70) comprises a filter chamber delineated by an annular plate (2) and two side plates (1, 1) and a vane (115) disposed within the filter chamber (3), the annular plates (2, 2) are disposed around a common center axis and the drive shaft (17) passes through the center axis of the annular plates (2, 2) and through the inside of the filter chambers (3), and is free to rotate with respect to the filter chambers (3), the vane (15) is fixed with respect to the drive shaft (17), extends in a radial direction towards the annular plate (2), and rotates in concert with the drive shaft (17), a supply path (50) supplying raw fluid to each filter chamber (3) is formed inside the drive shaft (17), the vane (15) has two side edges (15 a) facing the side plates (1, 1), and an end edge (15 b) facing the annular plate (2), at least one of the side plates (1, 1) of each filter unit (70) includes a filter element (4) for separating the raw fluid into a filtered fluid and a cake, the annular plate (2) includes an ejection port (7) for the cake, the ejection port is provided with a valve mechanism (8 a) which increases and decreases an amount of opening of the ejection port (7), the valve mechanism (8 a) comprises a rotating shaft (28 a) rotatably supported with respect to the ejection port (7), a damper (29 a) fixed to the rotating shaft (28 a) that opens and closes the ejection port (7), a cylinder (32) having a rod (33), and a lever (43) that links the rod (33) and the rotating shaft (28 a), converts reciprocating motion of the rod (33) to rotational motion of the rotating shaft (28 a), and transmits this motion, and an inflow pressure of the raw fluid from the supply path (50) into the filter chamber (3) and rotation of the vane (15) causes the filtered fluid to flow out from the filter element (4) to the outside of the filter chamber (3), a cake that remains inside the filter chamber (3) being pushed to the outside of the filter chamber (3) via the ejection port (7). 